Methods for detecting catecholamines by mass spectrometry

Abstract

Provided are methods for determining the amount of one or more of one or more of epinephrine (E), norepinephrine (NE), and dopamine (D) in a sample using mass spectrometry. The methods generally involve ionizing one or more of E, NE, and D in a sample and detecting and quantifying the amount of the ion to determine the amount of one or more of E, NE, and D in the sample.

That which is claimed is: 
     
       1. A method for determining the amount of one or more analytes selected from the group consisting of epinephrine, norepinephrine, and dopamine, the method comprising:
 a. performing a protein precipitation for a urine sample provided at a pH below about 3 to generate a supernatant; 
 b. subjecting the supernatant to electrospray ionization (ESI) under conditions suitable to produce one or more ions detectable by mass spectrometry; wherein:
 i. if one of the one or more analytes is epinephrine, said ionization comprises generating ions with a mass to charge ratio of 166.1±0.50; 
 ii. if one of the one or more analytes is norepinephrine, said ionization comprises generating ions with a mass to charge ratio of 151.9±0.50; and 
 iii. if one of said one or more analytes is dopamine, said ionization comprises generating ions with a mass to charge ratio of 136.9±0.50; and 
 
 c. determining the amount of the one or more ions by mass spectrometry, whereby 
 the amount of the one or more ions reflects the amount of said one or more analytes in the sample. 
 
     
     
       2. The method of  claim 1 , wherein the pH is at about 2.5. 
     
     
       3. The method of  claim 1 , wherein the urine sample is provided in a solution comprising sodium metabisulfite. 
     
     
       4. The method of  claim 1 , wherein the analytes are purified by high performance liquid chromatography (HPLC) prior to ionization. 
     
     
       5. The method of  claim 1 , wherein said mass spectrometry is tandem mass spectrometry. 
     
     
       6. The method of  claim 1 , wherein one of the one or more analytes is epinephrine. 
     
     
       7. The method of  claim 6 , wherein said ionization further comprises generating ions with a mass to charge ratio of 107.0±0.50. 
     
     
       8. The method of  claim 7 , wherein said ion with a mass to charge ratio of 166.1±0.50 is a precursor ion that is fragmented by tandem mass spectrometry to provide a fragment ion with a mass to charge ratio of 107.0±0.50. 
     
     
       9. The method of  claim 1 , wherein one of the one or more analytes is norepinephrine. 
     
     
       10. The method of  claim 9 , wherein said ionization further comprises generating ions with a mass to charge ratio of 107.0±0.50. 
     
     
       11. The method of  claim 10 , wherein said ion with a mass to charge ratio of 151.9±0.50 is a precursor ion that is fragmented by tandem mass spectrometry to provide a fragment ion with a mass to charge ratio of 107.0±0.50. 
     
     
       12. The method of  claim 1 , wherein one of the one or more analytes is dopamine. 
     
     
       13. The method of  claim 12 , wherein said ionization further comprises generating ions with a mass to charge ratio of 91.0±0.50. 
     
     
       14. The method of  claim 13 , wherein said ion with a mass to charge ratio of 136.9±0.50 is a precursor ion that is fragmented by tandem mass spectrometry to provide a fragment ion with a mass to charge ratio of 91.0±0.50. 
     
     
       15. The method of  claim 1 , wherein the amounts of two or more of the analytes from the group consisting of epinephrine, norepinephrine, and dopamine are determined in the same sample injection. 
     
     
       16. The method of  claim 1 , wherein the amounts of epinephrine, norepinephrine, and dopamine are determined in the same sample injection.